Re: [PATCH 4/5] nvme-tcp: support separate queue maps for read and write

[Sagi Grimberg]

+static int nvme_tcp_map_queues(struct blk_mq_tag_set *set)
+{
+       struct nvme_tcp_ctrl *ctrl = set->driver_data;
+       struct blk_mq_queue_map *map;
+
+       if (ctrl->ctrl.opts->nr_write_queues) {
+               /* separate read/write queues */
+               map = &set->map[HCTX_TYPE_DEFAULT];
+               map->queue_offset = 0;
+               map->nr_queues = ctrl->ctrl.opts->nr_write_queues;
+               blk_mq_map_queues(map);

Shouldn't this use nr_io_queues?

The intent is that HCTX_TYPE_READ will always use nr_io_queues and
HCTX_TYPE_DEFAULT will use nr_write_queues.. I'll document that
in the change log.

Also I find the reused local map variable a little odd and not helpful
for readability.  What about something like:

static int nvme_tcp_map_queues(struct blk_mq_tag_set *set)
{
        struct nvme_tcp_ctrl *ctrl = set->driver_data;

        set->map[HCTX_TYPE_DEFAULT].queue_offset = 0;
        set->map[HCTX_TYPE_DEFAULT].nr_queues = ctrl->ctrl.opts->nr_io_queues;
        blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);

        if (ctrl->ctrl.opts->nr_write_queues) {
                /* separate read/write queues */
                set->map[HCTX_TYPE_READ].queue_offset =
                                ctrl->ctrl.opts->nr_io_queues;
                set->map[HCTX_TYPE_READ].nr_queues =
                                ctrl->ctrl.opts->nr_write_queues;
        } else {
                /* mixed read/write queues */
                set->map[HCTX_TYPE_READ].queue_offset = 0;
                set->map[HCTX_TYPE_READ].nr_queues =
                                ctrl->ctrl.opts->nr_io_queues;
        }
        blk_mq_map_queues(&set->map[HCTX_TYPE_READ]);
        return 0;
}

That's better.. I'll update the patch with a change according to my
note above..